Field of the Invention
One or more embodiments setting forth the ideas described throughout this disclosure pertain to the field of motion capture sensors and analysis of motion capture data. More particularly, but not by way of limitation, one or more aspects of the invention enable a method for analysis of a baseball swing using data captured from a motion sensor on the bat.
Description of the Related Art
Methods for analyzing swings of a piece of equipment, such as a golf club, tennis racquet or baseball swings for example include video capture systems that record high speed video of a swing and that analyze the motion of the piece of equipment, club, racquet or bat, etc., and the player from the video. These systems are typically expensive and complex, and they are not portable. Another method is to attach a motion sensor to the piece of equipment, e.g., a bat, etc., and to analyze motion data captured by the sensor during the swing. A significant challenge for these sensor based solutions is interpretation of the sensor data. In particular, sensors typically capture data in a local reference frame defined by the sensor geometry. This sensor reference frame moves and rotates constantly throughout a swing. For example, for a baseball bat, this challenge is more complex since the bat has rotational symmetry around its long axis; thus the batter can hold the bat in multiple orientations while swinging, which changes the sensor data. This applies to other sports that involve a swing of a piece of equipment and any discussion oriented towards a bat herein is not limiting, and can be applied to any other type of equipment that involves a swing as well. There are no known methods that transform swing sensor data from a sensor based reference frame to a meaningful reference frame that is insensitive to these changes in orientation. Existing methods emphasize vector magnitudes (such as total swing speed) in defining swing metrics because these magnitudes are invariant to rotations in the sensor reference frame. However, individual components of sensor measurements along carefully chosen transformed axes provide more detailed and more physically meaningful information.
In baseball and related sports, the trajectory of specific point on the bat or other piece of equipment, for example the sweet spot, is of particular importance since this is the optimum location on the bat for striking the ball. There are no known methods that combine analysis of the sweet spot trajectory with a swing plane reference frame.
For at least the limitations described above there is a need for a swing analysis method using a sweet spot trajectory.